Methods and apparatus for fusionless treatment of spinal deformities

This patent application is a divisional of U.S. patent application No. 09/350,876 filed Jul. 9, 1999, now U.S. Pat. No. 6,287,308, which is a continuation-in-part of U.S. patent application Ser. No. 08/892,604, filed Jul. 14, 1997, now U.S. Pat. No. 5,951,553.

BACKGROUND OF THE INVENTION

The present invention concerns instrumentation and techniques for the treatment of spinal deformities. In particular, the inventive methods and devices accomplish this treatment without the need for fusion of the spine.

Surgical intervention for the treatment of injuries to, and deformities of the spine is approaching its first century. Nevertheless, the field of spinal surgery was not significantly advanced until the development of the hook and rod system by Dr. Harrington in the early 1950's. Dr. Harrington developed this system in Houston when he began care of children with progressive neuromuscular scoliosis secondary to polio. Until that time, the progressive scoliosis had been treated with external casts, which themselves yielded unacceptably high complication rates. After a decade of development, the hook and rod system evolved into the form that is known today as the Harrington Instrumentation.

The original primary indication for use of Harrington Instrumentation was in the treatment of scoliosis. Scoliosis is a deformity of the spine in the coronal plane, in the form of an abnormal curvature. While a normal spine presents essentially a straight line in the coronal plane, a scoliotic spine can present various lateral curvatures in the coronal plane. The types of scoliotic deformities include thoracic, thoracolumbar, lumbar or can constitute a double curve in both the thoracic and lumbar regions.

Early techniques for correction of scoliosis utilized a halo-traction device. In this technique, a halo is fixed to the skull and a vertical force is applied to the spine through the skull. In a halo-femoral traction approach, the patient is supine and traction forces are applied through a halo and a femoral pin. In a halo-gravity traction procedure, the patient sits in a wheelchair and a suspended weight applies a vertical force through the halo. In halo-pelvic traction, a pelvic ring is affixed to the patient and a series of threaded rods connect the cranial halo to the pelvic ring to apply an adjustable force separating the two rings. In procedures using the halo, the patient is either immobile or severely restricted in mobility.

To avoid the need for halos, various rod-based systems have been developed. Of course, the original rod system for correction of scoliosis is the Harrington System which utilized threaded and notched rods. In particular, a typical Harrington System utilizes a notched distraction rod and at least one threaded compression rod, with the distraction and compression rods being applied to the concave and convex portions of the curvature, respectively. In some procedures, a single distraction rod spans across several thoracic and lumbar vertebrae. The threaded compression rods are then used to stabilize the rod fixation. In other approaches, the compression rod spans across the convex portion of the curve, such as between T₆and L₂. In a Harrington procedure, a hook placed at the notched end of the distraction rod can be progressively advanced toward the cranial end of the rod to progressively correct the spinal deformation. At the same time, hooks engaged to the threaded compression rods can be drawn together on the convex side of the curvature to assist in the correction and to stabilize the instrumented spine.

In an additional step of the Harrington procedure, once the spine has been substantially corrected, transverse stabilization can be added between the two rods extending on opposite sides of the spine. Importantly, for long term stability, bone graft is placed along the instrumented vertebral levels to achieve fusion along that portion of the spine.

One drawback commonly associated with the Harrington System is that the rods are completely straight. As a result, patients in which a Harrington System has been used to correct a scoliosis condition have been left with the so-called flat-back syndrome. Specifically, in correcting the lateral curvature of the spine, the normal sagittal plane curvature is eliminated by the presence of a completely straight rod. In some cases, it has been found that the patient is better off retaining the scoliotic curvature than enduring the complications associated with flat-back syndrome. Another drawback is the requirement of bracing and casting.

To address these problems, subsequent rod-based systems have relied upon pre-bent spinal rods and multiple fixation sites. Specifically, the rods are bent to the normal thoracic kyphosis and lumbar lordosis in the sagittal plane. One such system is the Luque segmental spinal instrumentation. In the early 1980's, Dr. Luque pioneered a technique for segmental correction of abnormal spinal curvatures in which wires were used to affix vertebral levels to a pre-bent rod. These sublaminar wires are used to help draw the vertebrae toward the rod and ultimately to hold the vertebrae in position. In one approach using Luque instrumentation, a unit rod is provided which utilizes a single rod anchored at its ends to the ilium and bent at its cranial end so that two halves of the rod are oriented on opposite sides of the spinal column. The unit rod can then be used as a lever to straighten the spine, after which Luque sublaminar wires are used to fix the vertebrae to the unit rod.

As with the Harrington System, the final step of the Luque Instrumentation is frequently fusion of the instrumented spinal segments. There have been suggestions for instrumentation without fusion to correct scoliosis in younger patients, this technique was believed to permit further spinal growth. However, the results of this instrumentation without fusion were not very promising and led to certain complications, including loss of correction, reduced spinal growth and an unacceptable rate of instrumentation failure.

In yet another rod-based instrumentation system pioneered by Dr. Cotrel in France, a pre-curved rod is engaged to the vertebrae at the concave side of the abnormal curvature. The rod is then rolled about its axis to derotate the scoliotic curvature and at the same time provide the instrumented segments with the normal sagittal plane curvature. For instance, in the correction of thoracic lordoscoliosis, rolling of a pre-curved rod not only derotates the curvature in the coronal plane, it also transforms that scoliotic curvature into a physiological thoracic kyphosis. The rod is held to the vertebrae by a series of hooks, which are ultimately fixed to the rod once the derotation process is complete. To ensure a stable correction, an additional rod is added on the opposite side of the spinous process from the first rod. Members for transversely connecting the two rods create a rigid scaffold are attached. Again, in this procedure, bone chips are placed along the instrumented vertebrae to achieve fusion at the instrumentation site.

Other rod-based systems have been developed over the last several years that accomplish similar correction of spinal deformities, such as scoliosis. For example, the TSRH® Universal Spine System of Danek Medical, Inc. and the ISOLA® Spine System of AcroMed Corp. can be instrumented to the spine to correct various types of spinal deformities. In all of these rod-based Systems, the spinal rods are permanently fixed to the patient's spine. Of course, once fusion of all the instrumented levels has occurred, the original instrumentation is largely superfluous.

Other techniques that have been developed for correction of spinal deformities are performed anteriorly from the convex side of the abnormal curvature. In this technique, the intervertebral discs are removed and an osteotomy spreader is used to separate the adjacent vertebrae, thereby realigning the vertebral bodies in the coronal plane. A rod is attached to the spine via screws to maintain the correction. Fusion material, such as bone chips, are inserted into the widened intervertebral disc spaces to ultimately achieve fusion at those vertebral levels. Immobilization using an external cast or brace can be utilized while fusion is occurring.

A related technique involves Dwyer instrumentation that utilizes a flexible cable. In this technique, the cable is connected to the affected vertebrae on the convex side of the curvature. The cable is then shortened, thereby applying compression to the convex side of the curvature. Once the curvature has been corrected using the Dwyer cable, ancillary instrumentation, such as a Harrington rod, can be added for fixing and stabilizing the spine. In the Dwyer instrumentation, Dwyer clamps are pressed into the vertebral bodies to provide a seat for the insertion of Dwyer screws. The Dwyer screws define a channel through which the Dwyer cable can pass to perform the compression and ultimately the derotation of the abnormal curvature.

A similar approach is taken using Zielke instrumentation, except that the Dwyer cable is replaced by a pre-bent threaded rod. Application of the compressive forces to reduce the convex side of the curvature occurs by threaded nuts along the rod to translate the bone screws engaged to the vertebrae. Failed fusion because of residual deformity can be corrected by using posterior osteotomies which are closed and anterior wedges which are usually open. Following mobilization of the spinal segments by the osteotomies, then the spinal deformity can be corrected with instrumentation and then re-fused to maintain the correction.

While many techniques and instrumentation have been developed for the correction of spinal deformities, none of which we were aware prior to our invention, had been devised that could achieve the necessary correction without fusion of the instrumented vertebral levels. Moreover, some of the techniques resulted in an undesirable flat-back syndrome in which the normal sagittal plane curvature is eliminated. In addition, the prior systems greatly restrict the patient's normal mobility, and some restrict the growth of the spine. In the latter instance, some of the spinal instrumentation is not acceptable for use in younger patients.

A need exists for a technique and system to correct spinal deformities without the necessity of fusing the corrected vertebral segments. A need also exists for a system and technique that can accomplish this correction with minimal long-term invasion of the patient.

SUMMARY OF THE INVENTION

In order to address these unmet needs, a method and instrumentation are provided for correction of spinal deformities without the need for fusion of the corrected segments. In one aspect of the invention, a surgical technique is provided in which osteotomies are closed on the convex side of the curvature deformity and opened on the concave side of the curvature. Mechanical wedges are engaged within the open wedge osteotomies on the concavity of the curvature. The vertebral bodies will heal and form a unified body at the location of the closed osteotomies. In this manner, the normal coronal plane position of the spine is restored by elimination of the curvature deformity.

In a further aspect of the technique, the orientation of the opening or closing wedge osteotomies can be predetermined to achieve a normal curvature in the sagittal plane and normal spinal orientation in the coronal plane. For example, the addition of mechanical wedges into opening wedge osteotomies in the lumbar spine can be used to eliminate an abnormal lateral curvature while restoring the normal lordotic curvature of the lumbar vertebrae.

In a further aspect of the technique, connection elements or fasteners are engaged to each of the vertebrae in which an osteotomy has been performed. The connection element can then be engaged to an elongated member, such as a spinal rod, that has been pre-bent to the adjusted spinal curvature. The longitudinal member stabilizes the spine as the closing osteotomies heal and the mechanical wedges become integrated into the vertebrae having the opening wedge osteotomies. In this manner, the intervertebral discs are maintained intact. Moreover, and perhaps most significantly, none of the vertebral levels are fused together. Once the vertebral bodies have completely healed, the longitudinal member can be removed. With this feature of the inventive technique, the normal mobility of the patient's spine is restored since the intervertebral discs are not fused.

In another aspect of the invention, instrumentation is provided that can be used to perform the inventive technique. In one feature of the invention, the instrumentation includes a correction device that includes upper and lower anchors configured to penetrate a single vertebral body at substantially opposite sides of the body. In three illustrated embodiments of the instrumentation, the anchors are in the form of staples. In other illustrated embodiments, the anchors are in somewhat the form of a half staple or an adz. In all illustrated embodiments, a connection element is provided that extends between the upper and lower anchors and through the vertebral body. In one implementation, the connection element includes a threaded shank that engages a mating threaded boss on the lower anchor. In another implementation, the connection element has a threaded shank which is fixed to the lower anchor, and a head portion of the instrumentation is threaded onto the shank. In both implementations, the connection element can be used to provide a compressive force between the upper and lower anchors, thereby retaining their position and engagement with the vertebral body.

In the various implementations, the connection element includes a head portion adjacent the upper anchor. The head portion can be configured for connection to an elongated member used to stabilize the spine. In one embodiment, the head of the connection element is configured to engage an elongated spine rod. In another, it is configured for a spinal tethering function.

In accordance with a further feature of the invention, two types of correction devices can be provided. One correction device is utilized to close the closing wedge osteotomy in a vertebral body. In this correction device, the connection element is used to engage an upper and lower anchor to the vertebral body. In the second correction device, a mechanical wedge is attached to the lower anchor. The second correction device is thus used in maintaining the opened wedge osteotomies on the concavity of the curvature to be corrected. The mechanical wedge member is situated within the open space created by the opening wedge osteotomy. The anchors, stabilize the opening wedge osteotomy in a closing direction around the mechanical wedge as the vertebral body heals. In some mild cases, adequate correction may be achieved without intervertebral rods, plates, cabling or tethering, and a further embodiment of the invention for such cases, is disclosed.

In accordance with the present invention, a method is provided for correcting spinal deformities without the need ion fusion of the spine. A further object of the invention is accomplished by the technique and instrumentation that allows a stabilizing elongated member to be used only temporarily. This aspect provides the benefit that the elongated member, such as the spinal rod, can be removed once the instrumented vertebrae have healed, thereby restoring the normal mobility to the patient's spine.

Another object of the present invention is achieved by aspects of the technique and instrumentation that allows for adjustment of the spinal curvature in both the sagittal and the coronal planes. Still other objects and certain benefits of the invention will be discerned from the following written description of the invention together with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side perspective view of a correction device used in connection with the inventive method for treatment of spinal deformities.

FIG. 2 is a side perspective view of a second type of correction device used in this inventive technique, in which the correction device includes a mechanical wedge member for placement within an opening wedge osteotomy.

FIG. 3 is a top perspective view of a component of the correction device shown in FIG. 2, particularly showing the mechanical wedge member.

FIG. 4 is a top elevational view of the component shown in FIG. <b>3</b>.

FIG. 5 is an end elevational view of the component shown in FIG. <b>3</b>.

FIG. 6 is a side elevational view of the component shown in FIG. <b>3</b>.

FIG. 7A is a view of the anterior aspect of a portion of the lumbar spine showing a correction device as depicted in FIG. 2 engaged within a vertebra.

FIG. 7B is a view in the coronal plane of the instrumented vertebra in FIG. 7A with the correction device shown in cross-section.

FIG. 8 is a view from the anterior aspect of the spine of a vertebral level with a correction device as depicted in FIG. 1 engaged within the vertebral body.

FIG. 9 is a side elevational view of an alternative embodiment of a connection element for use with the correction devices shown in FIGS. 1 and 2.

FIG. 10 is a top elevational view of the connection element shown in FIG. <b>9</b>.

FIG. 11 is a schematic representation of a deformed spine and depicting the locations of opening and closing wedge osteotomies.

FIG. 12 is a view of the spine shown in FIG. 11 with the osteotomies opened and closed in accordance with the inventive technique.

FIG. 13 is a view of the corrected spine shown in FIG. 12 with the inventive instrumentation engaged to the instrumented vertebral levels.

FIG. 14A is a view of a vertebra in the coronal plane showing an axis for performing an osteotomy in conjunction with a method of the present invention.

FIG. 14B is an anterior to posterior view of the vertebra in FIG. 14A in which the osteotomy site is shown in cross-hatch.

FIG. 14C is a lateral view of the vertebra in FIG. 14A in which the osteotomy site is shown in cross-hatch.

FIG. 15 is a perspective view of a correction device according to the present invention and with further improvements.

FIG. 16 is a top plan view of a spinal rod receiving head of the correction device of FIG. <b>15</b>.

FIG. 17 is an elevational view of the correction device of FIG. <b>15</b>.

FIG. 18 is a partial sectional view of the device taken at line <b>18</b>—<b>18</b> in FIG. <b>17</b> and viewed in the direction of the arrows.

FIG. 19A is a view of the anterior aspect of a portion of the lumbar spine showing two of the correction devices of FIG. 15 engaged in adjacent vertebral bodies with a spinal rod fastened to them and shown fragmentarily.

FIG. 19B is a view of the correction device of FIG. 15 installed as in FIG. <b>19</b>A and viewed in the coronal plane.

FIG. 20 is an elevational view of another embodiment of the correction device.

FIG. 21 is a section through the device of the FIG. 20 embodiment taken at line <b>21</b>—<b>21</b> in FIG. <b>16</b> and viewed in the direction of the arrows.

FIG. 22 is a perspective view of the outer or top bone anchoring device of the FIG. 20 embodiment.

FIG. 23 is an elevational view thereof

FIG. 24 is a perspective view of the bottom or inner end bone anchoring device according to the FIG. 20 embodiment.

FIG. 25 is a plan view of the device of FIG. <b>24</b>.

FIG. 26 is a view similar to FIGS. 7A and 19A but illustrating application of the embodiment of FIG. <b>20</b>.

FIG. 27 is an elevational view of another embodiment of the correction device.

FIG. 28 is another elevational view of the device of FIG. 27 rotated on its axis 90°.

FIG. 29 is a section therethrough taken at line <b>29</b>—<b>29</b> in FIG. <b>8</b> and viewed in the direction of the arrows.

FIG. 30 is a elevational view of still a further embodiment of the invention useful in a tethering application.

FIG. 31 is an elevational view thereof with the device turned 90° on its axis.

FIG. 32 is a section therethrough taken at line <b>32</b>—<b>32</b> in FIG. <b>31</b> and viewed in the direction of the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to preferred embodiments thereof and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the invention, and such further applications of the principles of the invention as described therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

The present invention concerns apparatus and methods for use in the correction of spinal deformities without the need for fusion of adjacent vertebrae. In general terms, the inventive technique involves creating opening and closing osteotomies in the affected vertebrae. Wedges of material are either removed or added to each vertebra as needed to bring the vertebra into a normal spinal alignment. In another aspect of the technique, the opening/closing osteotomies are oriented in the vertebral body so as to effect curvature corrections in both the sagittal and the coronal planes.

The inventive surgical techniques can be accomplished by novel correction devices for a closing osteotomy. One such correction device can include upper and lower staples that are engaged on essentially opposite sides of the vertebral body. A connection member spans between the upper and lower staples to apply a slight compressive force to hold the staples in position. The connection member itself can threadedly engage the lower staple and can include an enlarged head to provide a reaction surface as the threaded shank of the connection member passes through an opening in the upper staple.

The opening osteotomy can be retained by a connection device that includes similar upper and lower staples. In one modification, the opening osteotomy correction device includes a mechanical wedge member attached to the lower staple. The wedge member fits within the osteotomy site to hold the osteotomy open and engage the vertebral body. A similar connection member is provided that can be threaded into the wedge member and that exerts a compressive force at an opening in the upper staple.

In both correction devices, the connection member can include a head portion that is adapted to engage an elongated member spanning the affected vertebrae. In one aspect of the invention, once the opening and closing osteotomies have been perfected by way of the correction devices, the connection members can be engaged to the elongated member, such as a spinal rod, to stabilize the construct. Once bone union is achieved at the osteotomy sites, the spinal rod can be removed to restore the normal motion of the vertebral segments.

With this general description in mind, specific details of the correction devices can be seen with reference to FIGS. 1-10. Looking first at FIG. 1, a correction device <b>10</b> is depicted that is used for the closing osteotomy discussed above. The correction device <b>10</b> includes a lower bone-piercing anchor <b>11</b>, an upper bone-piercing anchor <b>12</b> and a connection member <b>13</b>. The lower anchor, in the form of a staple <b>11</b> includes a pair of prongs <b>15</b> connected to and separated by a base plate <b>16</b>. The prongs <b>15</b> are configured to be pressed into the hard cortical bone of the vertebral body. Such prongs typically include a tapered cross-section to facilitate their insertion and can be of a configuration shown in U.S. Pat. No. 5,395,372, owned by the assignee of the present invention. The lower staple <b>11</b> also includes a threaded boss <b>17</b> projecting from the base plate <b>16</b> in the same direction of the prongs <b>15</b>. The boss <b>17</b> is preferably cylindrical and includes an internally threaded bore.

The upper anchor <b>12</b> of the correction device <b>10</b> is similarly formed like a staple by upper prongs <b>20</b> attached to an upper plate <b>21</b>. In accordance with the preferred embodiment, the upper staple <b>12</b> has a greater width between its prongs <b>20</b> than the lower staple <b>11</b>. In one specific embodiment, the upper staple <b>12</b> can have a width of about 2.0 cm between its prongs, while the lower staple <b>11</b> can have a width of about 1.5 cm between its prongs <b>15</b>. Of course, it is understood that the dimensions of the upper staple <b>12</b> and lower staple <b>11</b> are principally determined by the anatomy of the particular vertebra into which the staples are engaged. In the specific example above, the staples are sized for engagement within a lumbar vertebra. It is further understood that while in the preferred embodiment the upper staple is wider than the lower staple, both staples can have essentially the same width between their prongs.

The next element of the correction device <b>10</b> is the connection member <b>13</b>. The connection member <b>13</b> includes an elongated machine threaded shank <b>25</b> that bears external threads for mating with the internal threads of the boss <b>17</b> of the lower staple <b>11</b>. In one specific embodiment, the machine threaded shank <b>25</b> has a diameter of 0.30 cm with 5-40 UNC 2A machine threads. The internal threads of the boss <b>17</b> are similarly configured for mating with the threaded shank <b>25</b>. The length of the threaded shank <b>25</b> is determined by the vertebral anatomy. Preferably, the threaded shank <b>25</b> has a length sufficient to span substantially across the vertebral body. For firm engagement of the connection member <b>13</b> between the upper and lower staples, it is also preferable that the threaded shank <b>25</b> have a length sufficient to extend substantially completely into the threaded boss <b>17</b>. Likewise, it is also preferable that the threaded boss have a length that is sufficient for a solid threaded engagement between it and the threaded shank. In one embodiment, the threaded boss <b>17</b> has a length that is greater than half the length of the threaded shank <b>25</b>. In a specific embodiment, the threaded shank <b>25</b> can have a length of about 45 mm, while the threaded boss <b>17</b> of the lower staple <b>11</b> has a length of about 25 mm.

In a further aspect of the connection member <b>13</b>, an enlarged head <b>26</b> is provided. A shoulder <b>27</b> is situated between the head <b>26</b> and the machine threaded shank <b>25</b>. While the shank <b>25</b> is sized to fit through an opening <b>22</b> in the upper plate <b>21</b> of the upper staple <b>12</b>, the shoulder <b>27</b> has a diameter that is larger than the diameter of the opening <b>22</b>. In this manner, the connection member <b>13</b> can apply a compressive force between the upper and lower staples as the threaded shank <b>25</b> is threaded into the boss <b>17</b>. The shoulder <b>27</b> applies a force to the upper staple <b>12</b> to push it toward the lower staple <b>11</b>.

In a further aspect of the invention, the head <b>26</b> of the connection member <b>13</b> is configured for engagement to an elongated member extending along the spine adjacent the instrumented vertebrae. In accordance with the invention, the head <b>26</b> can assume a variety of configurations provided that it can be firmly engaged to the elongated member. In the embodiment shown in FIGS. 1 and 2, the elongated member is a spinal rod, such as a spinal rod provided with the TSRH® Spinal System. In the specific embodiment illustrated in FIG. 1, the head <b>26</b> is generally U-shaped defining a slot <b>29</b> between posts <b>33</b> forming the U-shape. The head <b>26</b> can also define tool recesses <b>30</b> on opposite sides of the posts <b>33</b> so that the head can be gripped by a tool useful in threading the shank <b>25</b> into the threaded boss <b>17</b>.

The head <b>26</b> further defines an engagement face <b>31</b> that is oriented toward the elongated member, or spinal rod. In a specific embodiment, the engagement face <b>31</b> includes a plurality of radial splines <b>32</b> emanating from the slot <b>29</b>. In this illustrated embodiment, the head <b>26</b> of the connection member <b>13</b> is substantially identical to the head of the Variable Angle Bone Screw sold by Danek Medical, Inc. This bone screw is also depicted in U.S. Pat. No. 5,261,909, owned by the Assignee of the present invention. Specific reference is made to FIG. 2 of the '909 patent and its accompanying description at column 4, lines 10-23, which figure and text are incorporated herein by reference. The '909 patent further describes one manner in which the head of the variable angle bone screw is engaged to a spinal rod. Specifically, reference is made to FIGS. 3-5 and the text at column 4, line 35 through column 5, line 47, which description is incorporated herein. To summarize, the head <b>26</b> of the connection member <b>13</b>, just like the head of the variable angle bone screw, is engaged to a spinal rod by way of an eyebolt and washer configuration. The washer includes splines that can mate with the splines <b>32</b> on the head <b>26</b>. The washer also engages the spinal rod and permits connection of the head <b>26</b> to the spinal rod at variable angular orientations. Again, the details of this type of variable angle connection are now well known as shown in the '909 patent.

While the correction device <b>10</b> is used for a closing osteotomy, the correction device <b>40</b>, depicted in FIG. 2, is provided for use in an opening osteotomy. Like the correction device <b>10</b>, the device <b>40</b> includes a lower staple <b>41</b> and an upper staple <b>42</b>. The lower staple <b>41</b> includes prongs <b>45</b> configured for penetration into the cortical bone of a vertebra. A base plate <b>46</b> connects the prongs <b>45</b>. Likewise, the upper staple <b>42</b> includes a pair of prongs <b>50</b> connected by an upper plate <b>51</b>. Like the upper staple <b>12</b>, the upper staple <b>42</b> also defines an opening <b>52</b> in the upper plate <b>51</b>. The correction device <b>40</b> also utilizes the connection member <b>13</b> which is, in the specific embodiment, identical to the connection member <b>13</b> shown in FIG. <b>1</b>. In that regard, the connection member <b>13</b> includes a shoulder <b>27</b> that prevents passage of the enlarged head <b>26</b> through the opening <b>52</b> in the upper plate <b>51</b> of the upper staple <b>42</b>. The connection member <b>13</b> also includes an elongated machine threaded shank <b>25</b>.

The connection device <b>40</b> further includes a wedge member <b>43</b> that is configured to be disposed within the osteotomy site to maintain the positioning of the portions of the vertebral body after the osteotomy is opened. Details of the lower staple <b>41</b> and the wedge member <b>43</b> that is engaged thereto, are shown in FIGS. 3-6. In one specific embodiment, the lower staple <b>41</b> includes a flat edge <b>47</b> and a curved edge <b>48</b>. The wedge member <b>43</b> includes a wedge body <b>55</b> that is preferably fixed to the lower staple <b>41</b>, such as by welding. The wedge body <b>55</b> defines a threaded bore <b>56</b> therethrough, that operates substantially similar to the threaded boss <b>17</b> of the lower staple <b>11</b> of the connection device <b>10</b> shown in FIG. <b>1</b>. In particular, the threaded bore <b>56</b> can have a similar thread configuration to the threaded shank <b>25</b> of the connection member <b>13</b>. A bore relief <b>57</b> is provided at the tapered end <b>61</b> of the wedge body <b>55</b>. This bore relief <b>57</b> is preferably formed by angled faces converging toward the threaded bore <b>56</b>. The relief <b>57</b> facilitates entry of the threaded shank <b>25</b> of the connection member <b>13</b> into the threaded bore <b>56</b>.

The wedge body <b>55</b> further includes a flat end face <b>58</b> that is aligned with the flat edge <b>47</b> of the lower staple <b>41</b>. On the opposite side of the wedge body <b>55</b> from the flat end face <b>58</b> is a curved face <b>60</b>, which also corresponds to the curved edge <b>48</b> of the lower staple <b>41</b>, both features being best shown in FIG. <b>5</b>. The curved face <b>60</b> preferably conforms substantially to the anterior perimeter of the vertebral body. The flat end face <b>58</b> is provided for clearance from the spinal foramen in the vertebra. It is understood, that in some specific embodiments, the wedge member <b>43</b> can be symmetrically shaped—that is, the wedge body <b>55</b> can include a curved end face, such as end face <b>60</b>, on both sides of the body.

In accordance with certain aspects of the invention, it is important that the wedge body <b>55</b> provide as large an area as possible for contacting the portions of the vertebral body at the osteotomy site. This contact occurs at the angled side faces <b>59</b>, which are best shown in FIGS. 3 and 6. The angled side faces <b>59</b> define an angle between each other that specifically corresponds to the amount of opening that is desired at the osteotomy site. In a specific embodiment, the angle between the angled side faces <b>59</b> is 15 degrees. In one specific embodiment, the wedge body <b>55</b> has a height of about 1.25 cm from the bore relief <b>57</b> to the lower staple <b>41</b>.

In a specific embodiment, the lower staple <b>41</b> can have a relief bore <b>49</b> aligned with the threaded bore <b>56</b> of the wedge body <b>55</b>. In this manner, the connection member <b>13</b> can have a length sufficient to partially extend into the relief bore <b>49</b> of the lower staple <b>41</b>. Further in this specific embodiment, the edge of the angled faces, and more specifically the curved end face <b>60</b>, is formed at a radius of 0.95 cm. Again, the dimensions of these features of the wedge member <b>43</b> can be modified depending upon the anatomy of the vertebra within which the wedge member is engaged. Moreover, if greater or lesser wedge angles are desired, the angle between the faces <b>59</b> can also be modified.

One specific manner of placement of the correction devices <b>10</b> and <b>40</b> is shown in FIGS. 7A, <b>7</b>B and <b>8</b>. Looking first at FIG. 8, the correction device <b>10</b> is shown positioned in the anterior portion of the vertebral body. In particular, the connection member <b>13</b> spans essentially laterally across the vertebral body, with the lower staple <b>11</b> and upper staple <b>12</b> penetrating the cortical bone of the vertebral body. Preferably, the staples have a width sufficiently narrow to keep them out of the adjacent discs D and fully contained within the vertebral body V. In the specific embodiment of the connection member <b>13</b>, the head <b>26</b> is oriented with its posts <b>33</b> aligned substantially within the coronal plane. In this manner, connection of the head <b>26</b> of the member <b>13</b> to a spinal rod by way of an eyebolt occurs with the spinal rod extending along the length of the spine.

Looking at FIGS. 7A and 7B, the correction device <b>40</b> is depicted engaged within a vertebral body V. Again, the correction device <b>40</b> extends transversely across the anterior portion of the vertebral body with the lower staple <b>41</b> and upper staple <b>42</b> penetrating the cortical bone. FIG. 7B illustrates the orientation of the wedge member <b>43</b> within the osteotomy site. It can be seen from this Figure that the curved face <b>60</b> approximates the anterior edge of the vertebral body V. The flat end face <b>58</b> then provides clearance for the vertebral foramen F so that the wedge member does not impinge upon the spinal cord within the foramen.

The connection devices <b>10</b> and <b>40</b> are preferably formed of a biocompatible sterilizable medical grade material. In some specific embodiments, the components of the correction devices <b>10</b> and <b>40</b> can be formed of stainless steel, while in other applications titanium can be the material of choice. In some embodiments, the wedge member <b>43</b> can be a solid member. In other embodiments, the wedge member <b>43</b> can be formed of a porous material, such as certain porous ceramics or a porous tantalum, such as HEDROCEL® produced by Implex Corporation. Alternatively, the wedge member <b>43</b> can include hollow portions with openings in the angled side faces <b>59</b> in contact with the vertebral body.

One object of these specific embodiments of the wedge member <b>43</b> is to permit tissue growth across and through the wedge member <b>43</b>. One goal of the procedure of the present invention is to achieve bone union of the portions of the vertebral body at the osteotomy sites. In the case where the osteotomy is closed, bony material is in direct contact so that bone union can occur fairly easily and rapidly. On the other hand, introduction of the wedge member <b>43</b> into an open osteotomy site can delay this bone union. Providing a wedge member <b>43</b> that allows for tissue growth through and/or into the wedge member can enhance the likelihood and rate of bone union of an open osteotomy site. In a specific preferred embodiment, the wedge member <b>43</b> is preferably formed of the porous tantalum HEDROCEL® material which not only permits bone growth through the wedge member <b>43</b>, but also allows the member to be fully integrated into the resulting bone union.

In an alternative embodiment, the connection member <b>13</b> for the correction devices <b>10</b> and <b>40</b> can be replaced by a connection member <b>65</b> as depicted in FIGS. 9 and 10. The connection member <b>65</b> includes a threaded shank <b>66</b> that can be identical to the threaded shank <b>25</b> of the connection member <b>13</b>. The primary difference between connection member <b>65</b> and the prior member is that the head <b>67</b> of member <b>65</b> is configured to directly receive a spinal rod therein. Specifically, the head <b>67</b> includes a pair of opposite arms <b>68</b> which form a U-shaped rod channel <b>69</b> therebetween. The rod channel <b>69</b> has a width and diameter that is just slightly larger than the diameter of a spinal rod so that the rod can be seated within the channel. The arms <b>68</b> further define an internally threaded bore <b>70</b> that intersects the rod channel <b>69</b>. A threaded plug (not shown) can be used to clamp the rod within the rod channel by threading into the threaded bore <b>70</b>. The head <b>67</b> of the connection member <b>65</b> of the present embodiment can be similar to the head of certain bone screws provided with the CD®, CCD® and CD Horizon® Spinal Systems sold by Sofamor, S.N.C., a subsidiary of Sofamor Danek Group. Some details of the construct can also be found in U.S. Pat. No. 5,147,360, assigned to Sofamor, S.N.C. Particularly, FIG. 5 of the '360 patent, together with the specification at column 4, lines 44-55, which disclosure is incorporated herein by reference, show one embodiment of a head of a bone screw for use with the present invention.

In the preferred embodiment, connection member <b>65</b> is preferred since it permits top-loading introduction of the rod into the head of the member when the correction devices <b>10</b>, <b>40</b> are implanted within the patient. It is understood that different head configurations for the connection members can be provided depending upon the type of elongated member extending along the length of the spine and the type of connection desired. For example, if the elongated member extending along the length of the spine is a plate, the head, such as head <b>26</b> of connection member <b>13</b>, can be in the form of a machine threaded post. This machine threaded post could then be engaged through a slot in the elongated plate by way of a nut. Such a connection is accomplished in the DYNALOK® bone bolt and plate sold by Danek Medical, Inc. Details of such a connection can also be found in U.S. Pat. No. 5,545,163, assigned to Danek Medical, Inc., and particularly in FIGS. 6 and 10 and their accompanying descriptive text, which is incorporated herein by reference. Alternatively, the head of the connection member can be closed, meaning that the elongated member spanning the length of the spine must be threaded through an opening defined in the head of the connection member. Regardless of the manner in which the connection member is engaged to a particular elongated member spanning the spine, in order to achieve one object of the invention, the elongated member should be capable of removal once bone union occurs at the osteotomy sites.

An example of using the correction devices <b>10</b> and <b>40</b> of the present invention, along with the inventive surgical techniques, can be understood with reference to FIGS. 11-14C. Referring first to FIG. 11, a portion of a patient's spine from T₃to the sacrum is shown in which the spine has a scoliotic curve. As can be seen in the Figure, the apex of the curve is offset a distance D from its correct alignment in the coronal plane. In other words, the spine is deformed laterally so that the axes of the vertebral bodies are displaced from the sagittal plane passing through the spine of the patient. It should be understood that the spinal deformity depicted in FIG. 11 is but one of many types of spinal deformities that can be addressed by the devices and techniques of the present invention. Most commonly the devices and techniques are expected to be used for either primary thoracic or thoracolumbar curves. They can be used for correction of the thoracic curve as an isolated curve, or the lumbar curve as an isolated curve.

In correcting the curved deformity shown in FIG. 11, wedge osteotomies R₆-R₁₁can be cut from the thoracic vertebra T₆-T₁₁at the convex side of the curvature. Preferably, a 15 degree osteotomy wedge of bone from the vertebral body is removed, although other wedge dimensions can be accommodated depending upon the amount of curvature and lateral offset of the particular vertebra. In the lumbar spine, opening osteotomies X₁-X₄are shown cut into the vertebra L₁-L₄. They could be cut into T₁₁to L₄. In the lumbar spine for this particular curvature, no bone material is removed. Instead, the vertebral body is essentially fractured to permit an opening osteotomy at that vertebral level. Again, the cut into the lumbar vertebrae occurs on the same side of the spine as the wedge osteotomies in the thoracic vertebrae. The various osteotomies in the thoracic and lumbar vertebrae can be performed using conventional tools and instruments, such as a chisel and an osteotomy spreader.

Once the osteotomy sites have been prepared in each of the affected vertebrae, the spine can be manipulated to close the closing osteotomies R₆-R₁₁and open the lumbar osteotomies X₁-X₄. The spine would then appear as shown in FIG. 12 in which the thoracic osteotomies are closed at sites C₆-C₁₁and the lumbar osteotomy sites are left open at sites W₁-W₄. In the configuration shown in FIG. 12, the lateral offset of scoliotic curvature is reduced to an offset D′ that is significantly less than the original curvature deformity. Ideally, the offset D′ would be negligible so that the spine would appear properly aligned in the coronal plane.

The determination of the location and nature of the opening and closing osteotomies can be determined after a review of A-P and lateral radiographs of the spinal deformity. In some senses, the identification of the osteotomies is a matter of geometry. For example, in the thoracic spine, each closing osteotomy will eliminate a certain amount of the abnormal curvature as the osteotomy is closed as shown in FIG. <b>12</b>. Similarly, each opening osteotomy in the lumbar spine will cause an effective translation of the particular lumbar vertebra toward the spinal midline. The amount of effective shifting of the axis of a lumbar vertebra toward the spinal midline can be based upon the size of the opening wedge osteotomy performed at that vertebra. It is, however, preferable that the opening or closing wedge osteotomies not exceed a 15 degree segment removed from or added to the vertebral body, in order to preserve the vertebral architecture as much as possible and to reduce the possibility of narrowing of the disc space.

Once the thoracic osteotomies are closed and the lumbar osteotomies are opened, the correction devices <b>10</b> and <b>40</b> can be engaged to the respective vertebrae. For example, the correction device <b>10</b> is engaged to the thoracic vertebrae, with the lower staples <b>11</b> positioned on one side of the vertebral body, and upper staples <b>12</b> positioned on the contra-lateral side of the vertebral body. The connection member, which can be member <b>65</b> in FIG. 9, is then engaged between the upper and lower staples. In preparation for engagement of the connection member <b>65</b>, a bore can be formed laterally through the vertebral body essentially through the centerline of the osteotomy. In certain techniques, the centerline of the osteotomy will extend laterally through the vertebral body and generally intersecting the center of the body. The bore can be prepared using a conventional drill or even using a curette.

A similar procedure is performed to introduce the correction device <b>40</b> to the lumbar vertebrae. In this instance, the wedge members <b>43</b> are disposed within the open osteotomy sites W₁-W₄. The lower and upper staples <b>41</b>, <b>42</b>, respectively, are then engaged to the vertebral bodies. The staples of both correction devices <b>10</b> and <b>40</b> are used to press the halves of the vertebral body together to close the osteotomy site as in the thoracic vertebrae, or to press the vertebral halves against the wedge member <b>43</b>. Prior to closing each of the osteotomies, bone fusion material or bone cement can be introduced into the osteotomy site to facilitate complete closure and ultimate bone union.

Once the correction devices <b>10</b> and <b>40</b> are engaged to their particular vertebrae, the elongated member, such as spinal rod <b>72</b>, can be engaged to each of the connection members <b>65</b> in the manner described above. Depending upon the configuration of the spine after performance of the osteotomies, the spinal rod <b>72</b> may be pre-bent to a particular curvature. In the configuration shown in FIG. 13, a certain amount of lateral curvature remains so that the rod would be pre-bent to emulate that lateral curvature. Further straightening of the spine can be accomplished if the rod <b>72</b> does not completely emulate the intermediate corrected curvature. In that instance, some widening and narrowing of the intervertebral disc space may occur, but it may be expected that the disc space height would be restored once the spinal rod <b>72</b> is removed.

In addition to any residual lateral curvature following the implantation of the correction devices, the spinal rod <b>72</b> is preferably bent to correspond to the normal kyphotic and lordotic curvatures of the thoracic and lumbar spine segments. In this manner, the flat back syndrome can be avoided. Care must be taken that the sagittal plane curvature of the spinal rod <b>72</b> not exceed the physiologic capability of the spinal segments. In other words, the deformed spine of a patient may also have a curvature deformity in the sagittal as well as the coronal planes. Under some circumstances, the rod rolling technique frequently utilized with the CD® Spinal System can also be implemented where an intermediate corrected residual curvature remains. In that instance, pre-bending the rod <b>72</b> to conform to that residual curvature, such as shown in FIG. 13, can also approximate the normal kyphotic and lordotic curvatures for a healthy spine. Thus, it can be contemplated that the rod <b>72</b> shown in FIG. 13 can be rolled about its axis so that the spine becomes perfectly aligned in the coronal plane with the restoration of the normal curvature in the sagittal plane. Also, separate rods and different rod locations may be used for addressing thoracic spine problems separate from lumbar spine problems.

In accordance with a preferred technique of the present invention, the correction devices <b>10</b> and <b>40</b> and the spinal rod <b>72</b> are implanted from an anterior approach. In contrast to prior techniques for the correction of scoliosis, only a single rod is required to maintain the stability of the correction. Since the physiology of the discs and vertebrae are not being changed, the elastic strength of the intervertebral discs will help retain the spinal column in its corrected configuration. Where each of the vertebral bodies is held together by way of staples on opposite sides of the body, there is substantially no risk that the osteotomy sites will separate or fail. Thus, it can be seen that the present invention takes advantage of the natural strength of the spine in order to retain the stability of the temporary fixation at least until bone union occurs. Depending upon the overall health of the patient and of the vertebral bodies, this bone union can occur in a manner of a few months.

Once bone union has occurred and the vertebral bodies are essentially healed, the spinal rod <b>72</b> is no longer essential to maintain the stability of the spine. In this case, the rod <b>72</b> can be removed by disconnecting it from each of the connection members <b>13</b> or <b>65</b>, leaving only the head of the connection member projecting beyond the vertebral body. At this point, the intervertebral discs resume their normal function and the patient's spinal column is as close to a normal configuration as possible. While the preferred embodiment of the invention envisions completely removing the spinal rod and associated connectors, such as eyebolts and machine threaded nuts, a biodegradable or resorbable rod can also be contemplated. In this instance, the rod would gradually resorb. Similarly, the correction devices <b>10</b> and <b>40</b> also become superfluous once bone union is achieved at the osteotomy site. Thus, the components of the correction devices can also be resorbable. One example previously discussed is the formation of the wedge member <b>43</b> out of a porous tantalum or HEDROCEL® material. A similar material may be usable to form the staples and the connection members, provided that the material forming these components can still meet their strength requirements.

In certain applications of the devices of the present invention, the spinal rod or elongated member may not be necessary to stabilize the instrumentation. For instance, if only a few vertebrae are instrumented with a correction device, the elongated spinal member or rod may not be required. Since the present invention contemplates correction of spinal deformities without fusion, additional fixation devices are not as essential as in other procedures in which fusion occurs. In those other procedures, the spinal segments must be essentially immobilized in order for the bony bridge to be formed across the intervertebral disc space. These same requirements are absent in the present inventive technique using the novel devices described above. In the instance in which a spinal rod is eliminated, it is of greater importance that the upper and lower staples hold their position within the vertebral body to thereby hold the osteotomy sites in their preferred orientation. Thus, the connection members <b>13</b>, <b>65</b> as previously described, provide a compressive force between the upper and lower staples to hold them within the vertebral body. It is understood, that this compressive force is not so great as to cause subsidence of the staples within the vertebral body. In cases in which the spinal rod <b>72</b> is not utilized, the connection member <b>13</b>, <b>65</b> does not require the presence of a head <b>26</b>, <b>67</b> which would ordinarily be engaged to the spinal rod. Instead, the connection member can be modified to simply include an enlarged shoulder <b>27</b> with a driving tool recess formed in the shoulder to receive a driving tool for threading the threaded shank <b>25</b>, <b>66</b> of the connection member into the threaded boss <b>17</b> or the threaded bore <b>56</b>. In the cases in which the spinal rod is eliminated, the vertebrae will be held in their corrected position by the elasticity of the intervertebral discs. Since the geometry of the vertebral bodies has been altered, the spine should automatically assume its corrected position, even without the assistance of an additional member spanning the spine.

The present invention also contemplates a surgical technique in which curvature deformities in multiple planes can be corrected. For instance, in many cases, the patient's spine suffers not only from scoliosis, but also from some degree of kyphosis or lordosis. In this instance, correction of an abnormal curvature must occur in two planes. The present invention readily permits such a correction.

As shown in FIG. 14A, the vertebral body V has an axis Z from the center of the vertebral body directed posteriorly and an axis Y directed laterally within the coronal plane. In cases where the particular vertebral body is misaligned in two planes, the centerline of the osteotomy <b>75</b> can be oriented at an angle α relative to the axis Y. In the procedures previously described, the centerline <b>75</b> of the osteotomy corresponds or is aligned with the axis Y. As can be seen in FIGS. 14B and 14C, removal of bone material for a closing osteotomy R, or addition of a wedge member for an opening osteotomy W is depicted. The angular orientation of the osteotomy at the angle α achieves correction and re-alignment of the vertebra in two planes.

Referring now to FIGS. 15-18, the correction device <b>80</b> is shown therein, is similar in many respects to that of FIG. <b>2</b>. For example, it includes a bone-piercing device <b>81</b> in the form of a staple very similar to the staple <b>42</b> in FIG. <b>2</b>. It also includes a bone-piercing device <b>82</b> at the opposite end and also in the form of a staple, although considerably modified in shape to better fit the surface of the intervertebral body as best shown in FIG. 19A, thereby matching the profile of the concave portion of the vertebral body. It also includes a wedge <b>83</b>, a screw <b>84</b>, and a head <b>86</b>. There are some differences which will be described now.

Viewed as shown in FIG. 18, the staple <b>82</b> described briefly above has a shape suggesting an inverted gull-wing or a wide “W”. The wedge <b>83</b> is fixed to the staple <b>82</b> by welding, press fit or any other suitable means at <b>87</b>. The wedge has a plurality of apertures <b>88</b> through it which serve to reduce mass and encourage bone growth through the wedge. The screw <b>84</b> is fixed to the wedge at <b>89</b> and/or staple <b>82</b> by welding, press fitting or otherwise.

The head <b>86</b> has internal threads which are threaded onto the external threads <b>91</b> extending from the outer end <b>92</b> of the screw. The head-end bone-piercing anchoring device <b>81</b> has a central aperture <b>93</b> through it, with a chamfer <b>94</b> at the top. The head has the outwardly opening U-shaped channel <b>96</b> opening at the outer end <b>97</b> thereof to receive a spinal rod such as <b>72</b> (FIGS. 13, <b>19</b>A, <b>19</b>B). There are also the usual tool receiver opening such as <b>98</b> and <b>99</b> that are usually provided for this type of head which has been in use by the assignee of the subject application and marketed under the assignee's CD Horizon® brand. The head may be of other shapes for other styles of devices for intervertebral attachment.

Further referring to head <b>86</b>, the oppositely facing flat outer surfaces <b>101</b>, and curved outer surfaces <b>102</b> blend into a base <b>103</b> having the concave surface blending from those faces into the base toward the inner end <b>104</b> of the base. This concave surface can successfully seat at the outer face <b>106</b> (FIG. 18) of the bone-piercing anchor device <b>81</b> without the surface <b>106</b> being in a plane perpendicular to the screw axis <b>85</b>. In this way, good anchorage in the vertebral body can be achieved even if one or the other of the two prongs of the piercing device <b>81</b> does not fully penetrate the vertebral body. Also it enables the outer portions <b>107</b>A and <b>107</b>B of surface <b>107</b> to contact the vertebral body, even if the axis of aperture <b>93</b> is not colinear with axis <b>85</b> of the screw. Here it should be mentioned that the head-end anchor <b>81</b> can be shaped such that, as viewed in the direction represented in FIG. 18, it would suggest a wide “M” or a gull wing appearance like that of anchor <b>82</b>, but not inverted. This could be used to conform the shape of the head-end anchor more closely to the profile of the vertebral body, if desired.

In the use of the FIGS. 15-18 embodiment of the invention, the procedure described above with reference to the lumbar spine in FIG. 11, can be followed. After performing the opening osteotomy and providing a hole through the vertebral body, the threaded end of the screw is inserted from one side of the vertebral body in the direction of arrow <b>111</b> in FIG. <b>19</b>A. Then, with the bone piercing anchor <b>81</b> installed loosely on the base <b>103</b> of the head <b>86</b>, the head is screwed onto the threads <b>91</b> of the screw <b>84</b>, with the first and second anchors <b>82</b> and <b>81</b> oriented as shown in FIG. <b>19</b>A. These devices are maintained in this attitude as the head is advanced on the screw threads until both the sharp edges of the prongs of the anchors are thoroughly seated in the vertebral body. Then the screw threads extending outward beyond the countersink <b>112</b> (FIG. 18) in the head, can be clipped or broken off with tooling already known in the art for performing that step with the CD Horizons instrumentation or other instrumentation known in the art. Bone fusion material or bone cement can be introduced into the holes <b>88</b> in wedge <b>83</b> prior to insertion of the screw, if desired, to enhance the function of whatever bone fusion material or bone cement may have already been introduced into the osteotomy site prior to installation of the screw.

After the desired correction devices have been installed in the vertebral bodies in the manner described above, the rod <b>72</b> as previously described, is installed in the slots <b>96</b> and clamped in place by the set screw <b>116</b> threaded into the threads <b>117</b> of the head <b>86</b> in FIG. <b>19</b>B. As shown in FIG. 19A, the inwardly facing surfaces <b>82</b>A and <b>82</b>B generally conform to the curvature of the concave side of the vertebral body. The bone-piercing edges <b>82</b>C of the device <b>82</b>, and which, when combined with the surfaces <b>82</b>A and <b>82</b>B present in FIG. 18 the appearance of “bird beaks”, are thereupon securely anchored in the vertebral body. Also, it should be noted in FIG. 18, that the sharp end <b>81</b>A and <b>81</b>B of the bone-piercing prongs of the member <b>81</b> are spaced at a slightly greater distance than at the bends <b>107</b>A and <b>107</b>B, providing a slight inward taper to assist this member <b>81</b> in anchoring in the bone and holding the bone snug against the angled side faces of the wedge.

Referring now to the embodiment in FIGS. 20 through 25, all of the features of this embodiment are the same as those in the embodiment of FIGS. 15-19B except for elimination of one of the prongs of each of the head-end bone-piercing device <b>121</b> and the wedge-end bone-piercing device <b>122</b>. The installation is much the same as described above for the embodiment of FIGS. 15-19B and shown in FIGS. 19A and 19B. As shown in FIG. 26, the preference is to have the bone-piercing device at each of the head end and wedge end of the assembly above the screw axis and the screw axis slightly below the coronal mid-plane of the vertebral body. As shown in FIG. 22, the upper bone-piercing member has a sharpened straight edge <b>121</b>A, like <b>81</b>A of the FIG. 15 embodiment and the central opening <b>123</b> with the upper edge chamfer <b>124</b> in the ring portion <b>125</b> of this device. The wedge end of bone-piercing device <b>122</b> has an aperture <b>126</b> through it which receives the wedge end <b>84</b>W of screw <b>84</b> which, as mentioned above, is identical to that in the FIG. 15 embodiment. Also as indicated above, the screw and wedge and bone-piercing device can be welded together or press fit or otherwise fixed together in any desired way such as welding at the bolt <b>26</b> in the wedge and bone anchor <b>122</b> and the hole <b>83</b>H in the wedge.

In the FIG. 26 installation, like those in FIGS. 7A, <b>7</b>B, <b>19</b>A and <b>19</b>B, the curved anterior edge <b>83</b>A of the wedge <b>83</b> conforms to the anterior perimeter of the vertebral body at the osteotomy site. The shape of the posterior edge <b>83</b>P, and the proximity of the edge <b>83</b>P to the screw axis, assure avoidance of the spinal foramen.

Referring now to FIGS. 27 through 29, this embodiment of the instrumentation is proposed for those cases in which the spinal deformity is sufficiently mild that reasonable correction can be obtained by opening wedge osteotomies, but without intervertebral connection. In this connection device <b>130</b>, there is the bone piercing device <b>131</b> virtually identical to device <b>121</b> in FIG. <b>20</b>. It is received on the screw <b>134</b> which has the lower bone piercing device <b>132</b> at the lower end, wedge <b>133</b> immediately above it, and a head <b>136</b> at the top. The lower bone piercing device <b>132</b> serves as an anchor in basically the same manner as described above with reference to FIG. <b>26</b> and is welded to the lower end <b>137</b> of the screw as at <b>138</b>, for example. The wedge <b>133</b> may be welded to the screw at <b>139</b> or to the anchor <b>132</b>.

The upper bone piercing device <b>131</b> has a central aperture <b>141</b> with a chamfer <b>142</b> at the upper edge of the opening on which is a convex surface <b>143</b> (typically spherical) of the head <b>136</b> is bearing when the head is screwed onto threads <b>146</b> with which the internal threads <b>144</b> of the head are mated. As described with reference to previous embodiments, the spaces between thread sets are narrowed so that, after installation of the connection device, and depending upon the distance between the two anchors, a portion of the upper end of the screw may extend beyond the top of the head <b>36</b> and can be broken off to provide a flush surface as shown in FIGS. 27 through 29.

As shown in FIG. 28, the wedge is shaped so that the anterior edge <b>133</b> will somewhat conform to the shape of the intervertebral body as shown for the wedge <b>83</b> in FIG. 19B for that embodiment of the invention. Also, the posterior edge <b>133</b>P of wedge <b>133</b> is close to the longitudinal axis of the screw to adequately space it from the spinal foramen. Apertures <b>147</b> in the wedge are provided for the same reason as discussed above.

Referring now to FIGS. 30 through 32, all features of this embodiment are the same as in the previously described embodiment except for the head. In this embodiment, while the head <b>151</b> has an external hexagonal surface as in the previously described embodiment, it is slightly different in the respect that the head is larger in a radial dimension with respect to the axis of the screw <b>134</b>. It also has a wall <b>151</b>W radially spaced from the screw axis and which has an aperture <b>152</b> through it. it. This embodiment of the present invention is intended for use in those applications where a metal cable or plastic tether such as of braided polyethylene may be used to make connections between the instrumentation of this type in one vertebral body, and that in another vertebral body. Such connections may be made between adjacent vertebral bodies, or vertebral bodies that are spaced from each other with other vertebral bodies in the space. As in the previously described embodiment, depending upon the distance of the anchors <b>131</b> and <b>132</b> after the instrumentation is installed in the vertebral body, if any portion of the upper end of the screw <b>134</b> extends above the shelf <b>153</b> of the head, that portion of the screw can be broken off.

It should be understood from the foregoing description of the embodiments of FIGS. 27 through 31, that the procedure for use is much the same as that described above with reference to FIGS. 15 through 26.

The present invention provides a surgical technique that permits correction of spinal deformities without the need for fusion of the intervertebral discs. The osteotomies conducted according to the technique can be done rapidly using conventional instruments while still protecting the spinal cord and controlling bleeding. The use of staples on opposite sides of the vertebral body maintain the osteotomy sites in their required configuration for bone union to occur. Ancillary support for the instrumented vertebrae can be provided by way of a removable elongated member spanning the spine, such as a spinal rod. Unlike prior techniques in which fusion of the disc space is performed, the spinal rod need not bear as much of the spinal loads as in the other procedures. Thus, the rod can have a smaller diameter than traditional spinal instrumentation rods. An ultimate goal of the present invention is removal of the spinal rod once bone union has occurred at the osteotomy site. The present invention contemplates application to a wide variety of spinal deformities, although correction of scoliosis may be a principal application.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.